The present invention generally relates to the production of electronic circuit cards wherein a number of individual electronic components are concurrently affixed to a card. The number of components being affixed may number into the hundreds and the absence of a single component will cause the circuit card to be defective. A vacuum pickup system is used to place each component onto the card being assembled. The present invention is a system for determining whether each vacuum pickup does in fact have an electronic component contained thereon. These electronic components may include integrated circuits, resistors, capacitors, or the like.
Conventional means of sensing components on vacuum pickup devices include using pressure transducers which sense the pressure differential created when air flows through a restriction in the vacuum device. Optical sensors and cameras have also been used to identify the presence of components on the vacuum pickup devices. For example, Scholten et al U.S. Pat. No. 4,683,654 utilizes an acoustic generator in the air flow path between the vacuum pickup and the vacuum source. In this manner, an audible sound is used to alert a system operator. Further, a microphone may be used to convert this audible sound into an electrical signal However, a signal processing unit including a high-pass filter, amplifier and limit value adjustment device must be utilized to process this signal transmitted from the microphone. The threshold value of the audible noise generated from the acoustic generator must be adjusted to a minimum value which will be processed and used to indicate the absence of a component on the vacuum pickup device. Additionally, due to improper adjustment of this threshold value and the presence of external noises, which will be present in the manufacturing environment contemplated by Scholten et al, inaccuracies may occur wherein erroneous indications regarding the presence of components are likely.
It would be advantageous to have a visual indication of the presence, or absence of a component on the end of a vacuum pickup device. This indication would be entirely independent of any extraneous noises and provide a reliable indicator of the presence or absence, of these components.